When the Doctor and Sarah Jane return to modern-day England, they find
London deserted and dinosaurs on the loose. It transpires that a group of
politicians and scientists are trying to right what they perceive as the
cause of all our planet's wrongs by reverting the Earth to a
pre-technological level. To make matters worse, they have help -- from
inside UNIT and amongst the Doctor's closest friends.

Production

On December 18th, 1972 -- shortly after recording was completed on his Frontier In Space -- Malcolm Hulke submitted a
new story idea entitled “Bridgehead From Space” to the
Doctor Who production office. This concerned the Doctor returning
to the present day to discover that aliens have invaded and ordered the
evacuation of London, claiming provocation by humanity. The aliens plan to
eventually convince mankind to cede to them all lands except for
Australia (in the manner of Hitler's tactics prior to World War II), which
they will then destroy.

At the same time, producer Barry Letts was keen to capitalise on the
success of the Drashig puppets employed in Carnival
Of Monsters. In particular, he thought that Doctor Who
could attempt a story set during the time of the dinosaurs, drawing on the
enormous popularity of the giant lizards with children. Letts conferred
with the Visual Effects department, who confirmed that this would be
within their capabilities. Script editor Terrance Dicks suggested that the
dinosaurs could instead be unleashed in modern times, and it was decided
that Hulke's storyline would be amended to have London terrorised by
dinosaurs instead of aliens. Letts and Dicks also suggested that Hulke
draw upon Mike Yates' betrayal of UNIT (under the influence of the
computer BOSS) in The Green Death, and have
him be one of the people responsible for the dinosaurs.

The BBC Visual Effects department confirmed that a story
involving dinosaurs was within their capabilities

Hulke's revised storyline was commissioned under the title
“Timescoop” on January 17th, 1973; the request for scripts
came on July 2nd. Shortly afterward, Serial WWW was retitled Invasion
Of The Dinosaurs. Richard Franklin was booked to play Yates on
September 5th, while Nicholas Courtney's services as Brigadier Lethbridge
Stewart were secured on the 14th.

Despite being planned as the second story of Season Eleven, Invasion Of
The Dinosaurs was the first to be made as part of Doctor Who's
eleventh recording block (The Time Warrior
having been taped at the end of the tenth block). It was also the second
serial in a row which Letts found himself wanting, but unable, to direct
because of his responsibilities to the adult science-fiction series
Moonbase 3. Instead, the director's chair was assigned to Paddy
Russell, whose last Doctor Who work had been The Massacre Of St Bartholomew's Eve seven years
earlier.

Unusually, Russell's first day of location filming, on September 2nd, was
unauthorised by the BBC or by the relevant officials. Intent on
establishing an appropriate atmosphere for the story, Russell and her
camera team -- posing as tourists -- visited several London landmarks
early in the morning to capture footage of the “deserted”
city. The main filming schedule spanned the 23rd to the 27th, plus the
29th, and took in a plethora of London locations.

The 23rd saw the debut of a new vehicle for the Doctor, replacing what
Hulke had originally written as a motorcycle in episode four. This was
“The Alien” (referred to in the scripts as the
“Whomobile”), a mock-hovercraft which Jon Pertwee had had
built earlier in the year. He had originally suggested its fabrication to
Letts, but when the producer vetoed the idea on the grounds of cost,
Pertwee financed it himself.

Two days for model filming then occurred on October 8th and 9th before
recording moved to the studio. As with most of the previous year, the
studio schedule for Invasion Of The Dinosaurs was divided into
fortnightly two-day sessions, taking place on Mondays and Tuesdays. The
first of these transpired on the 15th and 16th in BBC Television Centre
Studio 6. This concerned material for parts one and two, plus the
Underground segments for the fourth installment. By now, unfortunately, it
was clear that the dinosaur puppets -- the construction of which had been
contracted out to an external firm due to the size of the models -- were
far less convincing than the production team had anticipated. Because the
dinosaurs were such an important element of the story, however, these
flaws could not be minimised onscreen, leaving Russell and her team to
make do with what they had.

It became clear that the dinosaur puppets were far less
convincing than the production team had anticipated

More model shots were captured on the 18th, 19th and 20th before the
second studio session went ahead in TC8 on the 29th and 30th. This
involved the completion of episodes three and four, as well as the part
six sequence of Sarah Jane's imprisonment in, and escape from, the store
room. This was followed by two further days of model filming, on November
1st and 6th.

The last studio block occurred on November 12th and 13th in TC4, finishing
all the outstanding material from the fifth and sixth installments. George
Bryson, who had been cast as Private Ogden, proved unavailable for these
dates and so the character was replaced with Private Bryson
(unflatteringly described as “rather dim” in the revised
scripts), played by Colin Bell. For the first time in Doctor Who's
history, a “gallery only” day followed in late November. This
was a session involving none of the cast, allowing Russell and her team to
assemble the serial and complete work on electronic effects.

Letts latterly decided to keep the identity of the serial's monsters a
secret by airing the first episode under the truncated title
Invasion. This met with displeasure from Hulke, who thought that
the abrupt change of moniker with episode two, combined with the possible
loss of ratings due to the boring and generic title, was injurious to his
reputation. It was also an unsuccessful gambit, because considerable
advance publicity advertised the dinosaurs' appearance anyway. (The move
also lead to one of the most widely-believed myths in Doctor Who
folklore, with fans later believing that the reason behind the destruction
of only the print of the first episode of Invasion Of The Dinosaurs
was because it had been erroneously identified as part of the Patrick
Troughton story The Invasion.) Letts
subsequently apologised to Hulke, as did Head of Serials Ronnie Marsh.

Invasion Of The Dinosaurs would transpire to be Hulke's final
Doctor Who serial. Having tired somewhat of writing for the
televised programme, he found more joy in writing novelisations for
Target's Doctor Who range. In April 1979, Hulke fell ill and, after
suffering a relapse, died peacefully in hospital on July 6th of that
year.

Sources

Doctor Who: The Handbook: The Third Doctor by David J Howe and
Stephen James Walker (1996), Virgin Publishing, ISBN 0 426 20486 7.